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Vertical measurements of , and N2O concentrations, and uptake, and oxidation rates were measured at 5 sites in western Cook Strait, New Zealand, between 31 March and 3 April 1983. Nitrate increased with depth at all stations reaching a maximum of 10.5 μg-atom at the most strongly stratified station whereas was relatively constant with depth at all stations (~0.1 μg-atom ). The highest rates of oxidation generally occurred in the near surface waters and decreased with depth. N2O levels were near saturation with respect to the air above the sea surface and showed no obvious changes during 24 h incubation. oxidation by nitrifying bacteria may account for about 30% of the total utilization (i.e. bacterial+agal) and, assuming oxidation through to , may supply about 40% of the algal requirements of in the study area. These results suggest that bacterial nitrification is of potential importance to the nitrogen dynamics of the western Cook Strait, particularly with respect to the nitrogen demands of the phytoplankton. 相似文献
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The effects of sedimentation and compaction on oceanic heat flow 总被引:1,自引:0,他引:1
Iain Hutchison 《Geophysical Journal International》1985,82(3):439-459
Summary. The estimation of environmental effects forms an important part of the interpretation of oceanic heat flow measurements. In particular, the perturbations associated with sedimentation and surface temperature changes must be taken into account. Analytical solutions can be obtained only for individual, simplified versions of these problems, whereas any real example is complicated by the process of sediment compaction which changes the bulk thermal properties with depth. A physical model is developed which uses sediment porosity trends to predict the thermal parameters and material advection rates for an evolving sediment/basement system. These values are then used in a numerical solution to the heat flow equation to give estimates of the perturbed surface heat flux through time. In addition to variations in sedimentation rate, sediment type, radioactive heat production and surface temperature changes are considered. Heat flow corrections may vary by up to a factor of 2 according to sediment type while radioactive heat production can offset the effects of sedimentation by as much as 40 per cent. The results also indicate that alterations determined from simple analytical models tend to over-estimate the true perturbation to the flux. 相似文献
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Porites corals as recorders of mining and environmental impacts: Misima Island, Papua New Guinea 总被引:1,自引:0,他引:1
Stewart J. Fallon Jamie C. White†Malcolm T. McCulloch 《Geochimica et cosmochimica acta》2002,66(1):45-62
In 1989 open-cut gold mining commenced on Misima Island in Papua New Guinea (PNG). Open-cut mining by its nature causes a significant increase in sedimentation via the exposure of soils to the erosive forces of rain and runoff. This increased sedimentation affected the nearby fringing coral reef to varying degrees, ranging from coral mortality (smothering) to relatively minor short-term impacts. The sediment associated with the mining operation consists of weathered quartz feldspar, greenstone, and schist. These rocks have distinct chemical characteristics (rare earth element patterns and high abundances of manganese, zinc, and lead) and are entering the near-shore environment in considerably higher than normal concentrations. Using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), we analyzed eight colonies (two from high sedimentation, two transitional, two minor, and two unaffected control sites) for Y, La, Ce, Mn, Zn, and Pb. All sites show low steady background levels prior to the commencement of mining in 1988. Subsequently, all sites apart from the control show dramatic increases of Y, La, and Ce associated with the increased sedimentation as well as rapid decreases following the cessation of mining. The elements Zn and Pb exhibit a different behavior, increasing in concentration after 1989 when ore processing began and one year after initial mining operations. Elevated levels of Zn and Pb in corals has continued well after the cessation of mining, indicating ongoing transport into the reef of these metals via sulfate-rich waters. Rare earth element (REE) abundance patterns measured in two corals show significant differences compared to Coral Sea seawater. The corals display enrichments in the light and middle REEs while the heavy REEs are depleted relative to the seawater pattern. This suggests that the nearshore seawater REE pattern is dominated by island sedimentation. Trace element abundances of Misima Island corals clearly record the dramatic changes in the environmental conditions at this site and provide a basis for identifying anthropogenic influences on corals reefs. 相似文献
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Danny McCarroll Mervi Tuovinen Rochelle Campbell Mary Gagen Håkan Grudd Risto Jalkanen Neil J. Loader Iain Robertson 《第四纪科学杂志》2011,26(1):7-14
Twentieth‐century summer (July–August) temperatures in northern Finland are reconstructed using ring widths, maximum density and stable carbon isotope ratios (δ13C) of Scots pine tree rings, and using combinations of these proxies. Verification is based on the coefficient of determination (r2), reduction of error (RE) and coefficient of efficiency (CE) statistics. Of the individual proxies, δ13C performs best, followed by maximum density. Combining δ13C and maximum density strengthens the climate signal but adding ring widths leads to little improvement. Blue intensity, an inexpensive alternative to X‐ray densitometry, is shown to perform similarly. Multi‐proxy reconstruction of summer temperatures from a single site produces strong correlations with gridded climate data over most of northern Fennoscandia. Since relatively few trees are required (<15) the approach could be applied to long sub‐fossil chronologies where replication may be episodically low. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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Iain Hay 《The Professional geographer》2016,68(1):159-165
Although journal editing is central to scholarly enterprise, helping to maintain academic standards and shape disciplines, it is frequently discouraged within the academic assemblages that depend on it. Following recent contributions by geographers to discussions on academic service such as book editing and reviewing, this article explores some ironies and paradoxes of journal editing. It first discusses the challenges of journal editing as well as its problematic place in “academic capitalism.” It then examines professional and personal rewards of journal editing. Despite strong disincentives, journal editing offers valuable opportunities for self-development and deepening professional networks, as well as for refining the discipline. 相似文献